Just by the way superbat is horny and yearning and they fuck nasty about it. Bats accidentally gets Kent pregnant (they didn't know that could happen) and now they have to tell them JL that Superman is expecting and it's Bats'. (The JL thought they barely tolerated each other) (except for the batkids. They all knew and had found out separately beforehand)
OR Bats is transmasc stealth or intersex (either way he has a functioning womb) and got POUNDED on some great Kryptonian cock and now has to deal with all the side effects of being pregnant.And, of course, telling the JL that hes pregnant and it's Kryptonian.









